Python: String, list, tuple, dictionary

string:

All methods do not modify the value of the string, the string is the original value, but can be re-assigned; Use string methods to return a value

To use a looping string:

String method:

Name= "Hello World"
Print (Name.capitalize ()) #首字母大写
Print (Name.center, '-') #50个-put name in the middle
Print (Name.endswith (' U ')) #是否以x结尾, yes returns true
Number of print (Name.expandtabs ()) #补 \ t
Print (Name.find (' n ')) #查找字符串的索引, as with index usage, finds the return index and cannot find the return-1
Print (Name.format (name= ' Niuniu ', age=18)) #这个是格式字符串, and the first section of the blog has been written
Print (Name.format_map ({' name ': ' Niuniu ', ' age ':)) #这个也是格式化字符串, followed by a dictionary, the dictionary will be written in the back
Print (' abA123 '. Isalnum ()) #是否包含数字和字母
Print (' AbA '. Isalpha ()) #是否是英文字母
Print (' 122 '. IsDigit ()) #是否是整数
Print (' AA '. Isidentifier ()) #是否是一个合法的变量名
Print (' AA '. Islower ()) #是否是小写字母
Print (' AA '. Isupper ()) #是否是大写字母
Print (' LoadRunner book '. Istitle ()) #是不是一个标题 to determine if the first letter is capitalized
Print (' + '. Join ([' hehe ', ' haha ', ' ee ')) #拼接字符串, the elements of a reusable object (a string list dictionary, etc.) are stitched together with a single character
Print (Name.lower ()) #变成小写
Print (Name.upper ()) #变成大写
Print (' \nmysql \ n '. Lstrip ()) #默认去掉左边的空格和换行
Print (' \nmysql \ n '. Rstrip ()) #默认去掉右边的空格和换行
Print (' \nmysql \ n '. Strip ()) #默认去掉两边边的空格和换行
"MySQL". Strip (m), remove the M in MySQL
p = Str.maketrans (' ABCDEFG ', ' 1234567 ') #前面的字符串和后面的字符串做映射
Print (' CC AE GG '. Translate (p)) #输出按照上面maketrans做映射后的字符串
new_p = Str.maketrans (' 1234567 ', ' ABCDEFG ')
Print (' CC AE GG '. Translate (new_p))
Print (' MySQL is db. '. Replace (' MySQL ', ' Oracle ', 1)) #替换字符串, 1 represents the replacement of the first, does not specify the number of default replacements for all strings
Print (' MySQL is IsDB '. RFind (' is ')) #返回最右边字符的下标
Print (' 1+2+3+4 '. Split (' + ')) #切割字符串, returns a list. 1: Splits the string according to the specified string; 2: If there is nothing in the split brackets, divide by space
Print (' 1+2+3\n1+2+3+4 '. Splitlines ()) #按照换行符分割
Print (' Abcdef '. Swapcase ()) #大小写反转

Add:

Import string

Print (string.ascii_letters) #输出所有的大小写字母

Print (string.ascii_lowercase) #输出所有的小写字母

Print (string.ascii_uppercase) #输出所有的大写字母

Print (string.digits) #输出0到9的数字

list:

Lists are mutable variables

modifying values by subscript

Add value to list:

Adds an element from the specified location, and 0 represents the addition from the first element.

To delete a value from a list:

Del names deleting variables

Names.remove ("Yuansu"), remove removes the element from the list, POPs deletes the subscript of the pass

List method:

Only Pop has a return value

Sort

Nums.sort (): Sort nums list, default ascending
Nums.sort (reverse=true): Descending.
Reverse
Nums.reverse (): Reverse the value of the list

Count

Take the last value in the list: the subscript is-1, which represents the last element, 2 for the penultimate, and so on

Index

list Merge : Append extend differences:

Two listings a1,a2:a1.extend (A2): Add A2 elements to A1, A1 or one-dimensional arrays

A1.append (A2) adds the A2 array to the A1 as an element and A1 into a two-bit array

Multidimensional Arrays:

Take value: Get is Sex

slices:

Take a few elements out of a list or string

EG1: List: names=[' as ', ' SD ', ' DF ']
Print (Names[0:3]) #取第一和第二个元素, only take 0 and 1 subscript, Gu Tou regardless of the tail
Print (names[:]) #取所有的元素
Print (Names[:n]) #从第一个元素开始取到第n-1 elements
Print (names[n:]) #从n元素取到最后一个元素
Print (NAMES[A:B:C]) #从a取到b-1 elements, every C to take one time, do not write C by default one to take one, C is negative, the value is inverted, and the function of the reverse method, such as names[::-1], indicating the first value from the countdown to take the first , such as Names[8:1:-2]
EG2: string: name2= ' DFHID,DWD '
method, same as List

meta-group:

The value of the tuple cannot be changed, once created, it can no longer change the type is a tuple, the tuple is defined in (), the parentheses, the tuple has only two methods, that is, count and index, use the same list

tp= (1,2,3f,3,33re)

Print (Tp.count (3))

Print (Tp.index (3))

When defining tuples, if there is only one element, add commas, otherwise it will be considered str type. eg:a= (' abc ',)

Dictionary:

The dictionary is a Key-value data type, the dictionary definition uses {}, curly braces, each value is separated by ",", key and value are delimited with ":", key cannot be duplicated, and value is obtained by key

Two methods of value-taking:

Print (dic[' id ') and print (Dic.get (' id '))

Difference: 1, the value of the square brackets, cannot find the key value will be error, get value can not find no error, will return none. 2,get method can also pass a parameter, if get not to the key value, return parameters, such as print (Dic.get (' id ', ' Canshu ')), do not write default return None

Add key:

dic[' id ']=3
Dic.setdafault (' addr ', ' Beijing ')

Modify Key:

dic[' id ']=5 #同增加方式一样

Delete:

del dic[' id ']
Dic.popitem () #随机删除一个元素
Dic.pop (' id ') #字典是无序的, pop delete must pass a key value
Dic.clear () #清空字典

Built-in methods:

Print (All.keys ()) #返回所有的key
Print (All.values ()) #返回所有的value
Print (All.items ()) #返回所有的key和value, returns the Dict items type, in the loop, for example: for k,v in All.items ()
Print (k,v) #循环出所有的key和value, but because it is a dict_items type, the less efficient and efficient loop is: for the K in info:
Print (K,info[k]) #这样也是取所有的key和value, high efficiency
Info.update (Info2) #把两个字典合并, if you have the same key, take Info2 's value

To force type conversions:

Int () #转换成整型

Float () #转换成浮点型

STR () #转换成字符串

List () #转换成列表

Tuple () #转换成元组

Eval (' {' {' username ': 1} ') #用它来把字符串转成字典, the string must conform to the format of the dictionary

Python: String, list, tuple, dictionary